1. Field of the Invention
The present invention relates to a method of manufacturing a solar cell panel.
2. Description of Related Art
A method of manufacturing a solar cell panel is known, wherein the solar cell panel generates electric power by receiving sunlight. The method of manufacturing the solar cell panel includes: a process of forming a solar cell module; and a process of forming a panel using the solar cell module. In the process of forming the solar cell module, films used for solar cells are laminated on a transparency substrate and patterned by using laser etching or the like into a plurality of solar cells, which are integrated with series junctions. In the panel forming process, removal of the films located in a non-power-generating region, attachment of a cover sheet or the like, fitting of wires and a terminal box for drawing electric power, and the like are performed on the solar cell module to form a panel using the solar cell module. Moreover, in the panel forming process, the single substrate may be divided into a plurality of pieces, when necessary.
When the solar cell panel has adhesive substances or dirt (hereinafter may also be described as foreign substances) on a light incidence surface, light is interrupted by the foreign substances and a lower side of the foreign substances may become shady. Thus, this results in a decrease in the electric power generation. Particularly, in a thin-film solar cell panel in which thin-rectangular cells are connected in series and integrated, if a decrease in electric power generation is concentrated on some of the cells, these cells with decreased electric power become resistance for the entire panel, thus having an influence on an output decrease in the entire solar cell panel. Therefore, a substrate cleaning process is provided in manufacturing processes to remove the foreign substances. On the other hand, from a general viewpoint, an inspection of electric power generation on a solar cell panel in the manufacturing processes is performed, after confirming that visually checkable foreign substances of more than several tens of μm to 100 μm in size are removed such that the foreign substances do not become concentrated on a light incidence surface of the solar cell panel. In this case, small foreign substances of less than 100 μm in size are disregarded because they are considered to exert no influence.
In conjunction with the substrate cleaning, for example, Japanese Patent JP-P3057599B2 (corresponding to U.S. Pat. No. 5,894,853A) discloses one of techniques for substrate cleaning. JP-P3057599B2 discloses a cleaning apparatus including: a plurality of cleaning stages, reserving parts reserving cleaning fluids respectively used in the stages, and a passage mixing together the cleaning fluid reserved in the reserving part for one of the cleaning stages and the cleaning fluid reserved in the reserving part for the subsequent cleaning stage to supply the mixture to one of the cleaning stages.
In manufacturing solar cell panels as described above, an inspection of electric power generation is performed for quality control while the solar cell panels are manufactured or after the solar cell panels are completed. This inspection of the electric power generation is performed by measuring characteristics of electric power generation (current, voltage, output, and the like) while generating electric power through irradiation of simulated sunlight to the solar cell panel by a solar simulator.
Here, when the inspection of the electric power generation after the completion of solar cell panels is performed, results of the inspection vary and outputs of the solar cell panels decrease in some cases, although these solar cell panels are manufactured under identical conditions. The large variation in the results and the output decrease in the solar cell panels cause a reduction in a manufacturing yield of the solar cell panels. One of possible factors contributing to such variation in the results and such output decrease is influence of foreign substances adhering to a light incidence surface of the solar cell panel. However, even after a cleaning method is devised by a conventional method, the variation in the inspection results and the output decrease in the solar cell panels still remain.
That is, it is desired to provide a technique capable of performing an inspection of electric power generation with even higher accuracy without a variation in results and the output decrease in the solar cell panels under identical condition.
The inventors have now discovered the following fact. Various investigation tests performed by the inventors clarified that adhesion of fine foreign substances and dirt on the light incidence surface, which has not received any attention so far and has been hardly visually checked, has an influence on the inspection of the electric power generation performed with a solar simulator.
Generally, the solar cell panel is installed outdoors for use in electric power generation. In this case, under the outdoor sunlight, not only direct light but also scattering light enters the solar cell panel. Thus, even though adhesion of such small foreign substances and dirt, which are not visually checkable, blocks the light incidence on the solar cell panel, this little influences a performance of the electric power generation, thus resulting in no problem.
However, in particular, influence on accuracy of evaluation performed by an inspection device of electric power generation in a manufacturing process of the solar cell panel has been clarified.